The present invention relates to underwater pumping arrangements of the type including a submersible pump having a pump outlet conduit provided with a first connecting flange adapted to register with a second connecting flange of an outflow conduit permanently mounted at the bottom of a liquid-filled pit or container so as to form with the second connecting flange a seal-tight conduit joint, and being of the type in which the pump as it is lowered into the liquid-filled pit or container towards the bottom thereof is guided by guiding means, such as guide rails and/or cables, into a predetermined position in which the first connecting flange registers with the second connecting flange.
Submersible pump arrangements of this general type are known in a great variety of forms and designs. Likewise, the establishment of the seal-tight connection between the first and second connecting flanges, of the pump outlet conduit and of the permanently installed outflow conduit, respectively, can be effected in a great variety of known ways. However, despite the variety in the structural designs and in the procedures for establishing the seal-tight conduit joint, all the known structures and connecting procedures make use of a single principle: the force which is employed to press the first and second connecting flanges together to form the conduit joint is derived, in one way or another, from the inherent weight of the structure of the pump itself.
Federal Republic of Germany patent DT-PS No. 1,061,622 discloses one submersible pump arrangement of the type in question. In this arrangement, the first and second connecting flanges are each disposed at an acute angle relative to a vertical plane, with such an orientation that the inclined connecting flanges diverge from each other in downwards direction. Located intermediate the connecting flanges is a connecting member having correspondingly inclined flanges. The pump structure, after being lowered into position on the connecting member by means of vertically disposed guide rails, sits on the connecting member. Due to the inclined disposition of the flanges just mentioned, the weight of the pump structure itself maintains a seal-tight connection between the flange of the pump structure and of the connecting piece, in this way establishing the requisite conduit joint.
Federal Republic of Germany patent DT-PS No. 1,187,931 discloses a similar connecting expedient. To avoid the use of inclined connecting flanges, the lowering of the pump structure into the predetermined position relative to the outflow conduit structure is accomplished using a guide rail which at its lower end is inclined towards the outflow conduit structure. The pump structure is provided with guide rollers which ride upon the guide rail. As the pump structure rides along the vertical, upper portion of the guide rail, the pump structure is lowered vertically; as the pump structure continues to ride further down upon the inclined lower portion of the guide rail it is constrained to move into tight engagement with the outflow conduit structure. However, the constraining force, although directed by the inclined portion of the guide rail, is ultimately derived from the weight of the pump structure itself.
Federal Republic of Germany patent DT-PS No. 1,231,562 discloses another such submersible pump arrangement. In that arrangement, to establish the requisite seal-tight conduit joint, use is made of a mounting claw provided in the region of one of the connecting flanges and an engagement member provided in the region of the other connecting flange and adapted to be hooked over by the claw. The engagement member is formed as a resilient flexible rod. As the pump structure is lowered into place, under the control of guide cables, or the like, the claw hooks cover the engagement member. The resilient engagement member is caused to undergo a certain amount of stressing such that the upper edge of the connecting flange of the pump structure is pulled into seal-tight engagement with the connecting flange of the outflow conduit structure. Because of the resilience of the engagement member, manufacturing tolerances are not particularly critical in ensuring a reliable establishment of a seal-tight conduit joint. However, as before, the force which presses one connecting flange against the other is derived from the inherent weight of the pump structure itself, which is unsupported except at the end thereof provided with the connecting flange. When the force employed to establish and maintain the seal-tight connection is derived from the inherent weight of the pump structure itself, important disadvantages result. Firstly, the connecting flanges and neighboring structure are subjected to the heavy loading associated with the often very considerable weight of the pump structure. As a result, the known procedures for establishing the conduit joint can be employed only up to a certain maximum weight of the pump structure, because otherwise the connecting flanges will have to be excessively massive and strong. Accordingly, if the pump structure is of considerable weight, it would seem desirable to support the pump structure directly upon the bottom of the liquid-filled container or pit. However, this of course means that the inherent weight of the pump structure will no longer be available for the establishment and maintenance of the seal-tight conduit joint.
Federal Republic of Germany allowed patent application DT-AS No. 1,653,431 discloses an underwater pumping arrangement in which the outflow conduit structure is permanently mounted at the bottom of the liquid-filled pit or container and in which the pump structure is supported on a saddle structure which in turn is directly supported on the bottom of the pit or container. To establish the seal-tight conduit joint between the first and second connecting flanges, use is made of a wedge-like connecting conduit structure which is forced in between the first and second connecting flanges. The forcing in of the wedge-like connecting structure is accomplished from above using a threaded-rod drive. All this additional structure is expensive and undesirable in itself. Furthermore, however, it necessitates insertion and removal of the wedge-like connecting structure by manual operation; i.e., the seal-tight conduit joint is not automatically established without a separate manual operation. Also, the requirement for a threaded-rod drive is disadvantageous per se, since the pits into which such pump structures are lowered may be as deep as 80 meters.